<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		#div1{
			width: 50px;
			height: 100px;
			background: #ccc;
			margin-top: 5px;
			display: none;
		}
		#btn1{
			border-style: none;
			width: 50px;
			height: 20px;
			background-color: blue;
		}
		#btn1:hover{
			background-color: yellow;
		}
	</style>
	<script type="text/javascript">
		function show(){
		var oDiv=document.getElementById('div1');
		if(oDiv.style.display=='none')
			{oDiv.style.display='block'}
		else
			{oDiv.style.display='none'}
	}
	</script>
</head>
<body>
	<div id="btn1" onclick="show()">
	</div>
	<div id="div1">
	</div>
</body>
</html>